Differing literary and colloquial readings for certain Chinese characters are a common feature of many Chinese varieties, and the reading distinctions for these linguistic doublets often typify a dialect group. Literary readings (/) are usually used in loanwords, names (geographic and personal), literary works (like poetry), and in formal settings, while colloquial/vernacular readings (/) are usually used in everyday vernacular speech. For example, in Mandarin, the character for the word "white" () is normally read with the colloquial pronunciation bái (), but as a name or in certain formal or historical settings it can be read with the literary pronunciation bó (). This example is particularly well known due to its effect on the modern pronunciation of the names of the Tang dynasty (618–907) poets Bai Juyi and Li Bai (alternatively, "Bo Juyi" and "Li Bo"). The differing pronunciations led linguists to explore the linguistic strata. It is generally believed that the colloquial readings represent a substratum, while their literary counterparts a superstratum. Such differences reflect a history of dialect mixing and the influence of education and instruction on the area. Characteristics For a given Chinese variety, colloquial readings typically reflect native phonology, while literary readings typically originate from other Chinese varieties, typically more prestigious varieties. Colloquial readings are usually older, resembling the sound systems described by old rime dictionaries such as Guangyun. Literary readings are closer to the phonology of newer sound systems. In certain Mandarin and Wu dialects, many literary readings are the result of Nanjing Mandarin or Beijing Mandarin influence in the Ming and Qing dynasties. Literary readings are usually used in formal settings because past prestigious varieties were usually used in formal education and discourse. Although the phonology of the Chinese variety in which this occurred did not entirely match that of the prestige variety when in formal settings, they tended to evolve toward the prestige variety. Also, neologisms usually use the pronunciation of prestigious varieties. Colloquial readings are usually used in informal settings because their usage in formal settings has been supplanted by the readings of the prestige varieties. Because of this, the frequency of literary readings in a Chinese variety reflects its history and status. For example, before the promotion of Modern Standard Chinese (Mandarin), the Mandarin dialects of the Central Plain had few literary readings, but they now have literary readings that resemble the phonology of Modern Standard Chinese. On the other hand,